The present invention relates to vessels. More particularly, the present invention relates to a vessel having a variable draft, such that the vessel may be configured to operate in shallow waters and in deep waters.
Vessel hulls have traditionally been designed for specific uses, such as for use in shallow waters or in deep waters. Different hull designs provide for optimal operating characteristics for different uses. Shallow-draft vessels, for example, often have hulls that are relatively “flat” to maximize displacement and minimize draft, whereas deep-draft vessels often have v-shaped hulls that provide deep draft for desired seakeeping (e.g., good seakeeping providing low undesired motion, such as vertical motion or rocking).
More specifically, shallow-draft vessels are often designed with flat bottom hulls to provide the ability to navigate in relatively shallow waters, such as in shallow-water harbors, along rivers, along shorelines and in other bodies of shallow water. Shallow-draft vessels are also designed to maximize payload carrying capacity and to provide for simplified on-loading and off-loading of cargo. Examples of shallow-draft vessels include landing craft mechanized (LCM) and landing craft utility (LCU) that are often used by amphibious military forces to transport equipment and troops from sea to beachheads and/or to piers.
Shallow-draft vessels typically have relatively high water resistance due in part to large beam to length ratios, large wetted surfaces, and blunt water contact. Such characteristics provide for the generation of large amounts of resistance, such as turbulence and/or Kelvin wake, and high power requirements. Accordingly, shallow-draft vessels typically have poor seakeeping, poor ride, and poor handling characteristics. Due to these and other operational characteristics, shallow-draft vessels typically are not suited for use in deep water.
Alternatively, deep-draft vessels are often designed with v-hulls having relatively low beam to length ratios to provide the ability to navigate the vessels in deep waters, such as in the oceans and seas. Deep-draft vessels are often designed to provide desired seakeeping (e.g., good seakeeping providing low undesired motion, such as vertical motion or rocking) in high sea states. Deep-draft vessels, however, are typically not available for shallow-water use, such as docking in shallow harbors, river use, and navigation adjacent to shorelines, as the vessels may run-a-ground in these waterways.
A variety of operations require the use of vessels in both shallow and deep waters. As traditionally designed vessels typically have features that provide for optimized use in either shallow water or deep water, but not both, traditionally designed vessels do not provide optimal operating characteristics for both shallow and deep-water use.
Therefore, there is a need for vessels that may be operated in both shallow and deep waters, that provide for desired seakeeping and high speed operation in high sea states, and that provide high cargo carrying capacity with effective shallow-water operability.